Gas Exchange
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H.6.1 Define Partial Pressure.

            Partial Pressure is the pressure exerted by each component in a mixture.  The pressure of a gas in a mixture is the same as it would exert if it occupied the same volume alone at the same temperature (Dalton’s Law).

H.6.2 Explain the oxygen dissociation curves of adult and fetal hemoglobin and myoglobin.

            As the curves shift to the right, hemoglobin releases oxygen more easily.  It shows at what tension of oxygen the hemoglobin or myoglobin is saturated with oxygen.  When the first molecule of oxygen bides to the hemoglobin, it does so with difficulty.  Once it has bound, it distorts the shape of the pigment, so that the other 3 o2 molecules are taken up more easily.  As the oxygen tension increases, the ability to bind oxygen increases.  Oxyhemoglobin is carried in the blood to respiring tissues where the oxygen tension is lower.  Therefore, the oxyhemoglobin breaks down and delivers the oxygen to the tissues. 

            Fetal Hemoglobin is different because of its function.  The fetal hemoglobin (in order to survive) has to have a higher affinity for oxygen that the adult so that it can extract oxygen from the placenta.

H.6.3 Describe ways in which carbon dioxide is carried by the blood including the action of carbonic anhydrase, the chloride shift, and buffering by plasma proteins.

            Carbon dioxide is transported in the plasma.  85% of it is in the form of HCO3- ions.  An enzyme on the red blood cell, called carbonic anhydrase, combines these ions with water to form Carbonic acid.  It accelerates the process of forming H2Co3.

            The H+ ion released is buffered by the hemoglobin, preventing the blood from becoming too acidic and causing oxyhemoglobin to dissociate thereby giving up oxygen.  Membranes of a red blood cell have a sodium pump which pumps NA ions out, these combine with the HCO3, forming a NAHCO-.  Also, some of the CO2 in the blood also reacts with blood proteins.  

H.6.4 Explain the role of the Bohr Shift in the supply of oxygen to respiring tissues.

            As Co2 increases, the affinity for O2 decreases.  Co2 released in tissues causes the delivery of oxygen to increase as well because it has a higher affinity to the hemoglobin than oxygen.  Known as the Bohr effect.

H.6.5. Explain the mechanism of ventilation of the human lungs including the action of the internal and external intercostals muscles, the diaphragm and the abdominal muscles.

            Ventilation includes inspiration and expiration.  Inspiration is when you breathe in.  The diaphragm muscle contracts and flattens.  The external intercostals muscles contract making the ribs and sternum go up.  The volume increases making the pressure decrease, so air flows in.

            Expiration is when you breathe out.  The diaphragm muscle relaxes and becomes dome-shaped.  The external intercostals muscles relax making the ribs and sternum go down.  The volume of the lungs decreases, the pressure increases and air flows out.

H.6.6 Outline the possible causes of lung cancer and asthma and their effects on the gas exchange system.

            Causes of lung cancer: smoking, because of the carcogenes which induces changes in alveoli cells.  Causes a strain on the heart, and makes the elastic fibers become less elastic.  More residual air in lungs, and breather can not exhale as he can inhale. 

            Causes of asthma: hereditary, attacks can be triggered by allergens like pollen and dust.  It inflames and constricts the bronchial tubes which lead to wheezing and coughing. 

H.6.7 Describe the technique of mouth to mouth resuscitation. 

            The objective is to ventilate the lungs of a person who is not breathing.  Expired air still contains 16% of oxygen, can be used by patient.  Steps:

                        -clear airway (remove obstructions from head, face, neck, and mouth)

                        -Head of patient tipped back (patient on their back)

                        -Nose of patient pinched

                        -Mouth placed against patient’s mouth

                        -Air breathed into patients lungs

H.6.8 Explain the problem of gas exchange at high altitudes and the way the body acclimatizes. 

            At high altitudes, there is less oxygen in the air, which means that less is absorbed.  The concentration gradient between air in alveoli and blood is less so more air has to be taken in to do gaseous exchange. 

Other Notes in this Category

1. Gas Exchange
2. Homeostasis Basics
3. The Functions of the Liver
4. Transport

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